Central Bureau for Astronomical Telegrams
IAUC 4852: 1989o; TIME ADJUSTMENT ON 1989 Dec. 31
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Circular No. 4852
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
PERIODIC COMET BRORSEN-METCALF (1989o)
D. Jewitt, University of Hawaii; and Jane Luu, Massachusetts
Institute of Technology, write: "We have detected continuum
emission from P/Brorsen-Metcalf at submillimeter wavelengths, using
the 15-m James Clerk Maxwell Telescope on Mauna Kea. We believe
that this is the first submillimeter continuum detection of any
comet. A preliminary estimate of the 0.8-mm flux density is 90
+/- 18 mJy, measured in a 20" diameter diaphragm on Sept. 10.7 UT.
The flux density at 1.1 mm was 48 +/- 13 mJy on the same date. The
measured spectrum is consistent with Rayleigh-Jeans emission
(spectral index 2), as might be expected for millimeter-sized and
larger particles. The flux densities indicate emission from about
10E8 kg of millimeter-sized and larger dust grains. JCMT
measurements on the two preceding days show that the millimeter
emission varies by at least a factor of three from day to day."
D. K. Lynch and R. W. Russell of the Space Sciences Laboratory,
The Aerospace Corporation, communicate: "We obtained thermal
infrared spectroscopy and bolometry using the Infrared Telescope
Facility during Sept. 4-6, 6-8 days before perihelion. The
observations were made with the AT-1 Circular Variable Filter
(spectral resolution lambda/(Delta lambda) = 50, a north-south
chop of 60") and with the bolometer 'Bolo1', both using a 9"
aperture. The spectrum showed a smooth, featureless continuum
between 9 and 12.8 microns with no evidence of either silicate
emission or the 12.2-micron feature first seen in comet Wilson
1987 VII. The narrowband 10.3-micron magnitude was +0.50 and the
L and M magnitudes were 5.4 and 3.0 respectively. The color
temperature measured with L, M, and [N'] was between 350 and 500 K.
There was no evidence for variability during the 3-day period.
Imagery at 10 microns (3" aperture) showed a concentrated
inner coma slightly elongated in the direction of the tail."
TIME ADJUSTMENT ON 1989 DECEMBER 31
Bulletin C1 of the International Earth Rotation Service
announces that a positive leap second will be introduced such that
the sequence of UTC second markers will be: 1989 Dec. 31d23h59m59s,
31d23h59m60s, 1990 Jan. 1d00h00m00s. From 1988 Jan. 1 to 1989 Dec. 31,
the difference UTC-TAI = -24s; beginning 1990 Jan. 1, UTC-TAI = -25s.
1989 September 13 (4852) Daniel W. E. Green
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